1. Field of the Invention
The present invention relates to a steering angle control apparatus for a vehicle, for controlling the turning angle of the wheels which is caused in response to the steering output from tie rods of a steering unit.
2. Description of the Related Art
An apparatus disclosed in Published Unexamined Japanese Patent Application No. 64-22611 is known as a steering angle control apparatus of this type. In this example, the mounting positions of suspension arms on a vehicle body are displaced in the width direction of the vehicle in accordance with the vehicle speed and the turning angle of the wheels. When the turning angle is large, the suspension arm connected to the inside wheel is displaced outward in the width direction of the vehicle body, thereby increasing the maximum turning angle of the inside wheel. Therefore, the minimum turning diameter of the vehicle can be reduced.
In the conventional control apparatus described above, the mounting positions of the suspension arms on the vehicle body are displaced in the width direction of the vehicle body by means of an actuator. For this reason, the suspension mechanism as a whole must be displaced in this direction, so that large control force is required for displacing the arm mounting positions, thereby making the apparatus bulky.
In addition, since the arm mounting positions are controlled in accordance with the vehicle speed and the turning angle of the wheels, characteristics of the wheel alignment with respect to the vertical movement of the suspensions greatly change in response to the position control, and stable suspension performance cannot be assured.